One known type of information storage device is a disk drive device that uses magnetic media to store data and a movable read/write head that is positioned over the media to selectively read from or write to the disk.
FIG. 1a illustrates a typical disk drive unit 2 and shows a magnetic disk 201 mounted on a spindle motor 202 for spinning the disk 201. A voice coil motor arm 204 carries a head gimbal assembly (HGA) 200 that includes a slider 203 incorporating a read/write head and a suspension 213 to support the slider 203. A voice-coil motor (VCM) 209 is provided for controlling the motion of the motor arm 204 and, in turn, controlling the slider 203 to move from track to track across the surface of the disk 201, thereby enabling the read/write head to read data from or write data to the disk 201. In operation, a lift force is generated by the aerodynamic interaction between the slider 203, incorporating the read/write head, and the spinning magnetic disk 201. The lift force is opposed by equal and opposite spring forces applied by the suspension 213 of the HGA 200 such that a predetermined flying height above the surface of the spinning disk 201 is maintained over a full radial stroke of the motor arm 204.
FIG. 1b shows a perspective view of a slider shown in FIG. 1a, and FIG. 1c shows a top plan view of the slider of FIG. 1b. As illustrated, the slider 203 comprises a leading edge 219 and a trailing edge 218 opposite to the leading edge 219. A plurality of electrical connection pads 215, for example four electrical connection pads are provided on the trailing edge 218 for electrically connecting the slider 203 to the suspension 213 (as shown in FIG. 1a). The trailing edge 218 also comprises a pole tip 216 incorporating a magnetic read/write head on its central position for achieving data reading/writing operation of the slider 203 with respect to the disk 201. The pole tip 216 is formed on the trailing edge 218 by suitable manner such as deposition. In addition, an air bearing surface pattern 217 is formed on one surface of the slider 203 perpendicular to the trailing edge 218 and the leading edge 219.
As shown in FIG. 1d, the pole tip 216 has a layered structure and comprises from top to bottom a second inductive write head pole 116, a first inductive write head pole 118 spacing away from the second inductive write head pole 116, a second shielding layer 111 and a first shielding layer 113. All above components are carried on a ceramic substrate 122 that is used for controlling flying height of the slider. A magneto-resistive element (MR element) 112, along with a lead layer 114, which is disposed at two sides of the magneto-resistive element 112 and electrically connected to the magneto-resistive element 112, is provided between the second shielding layer 111 and first shielding layer 113. Referring to FIG. 1e, coils such as copper coils 117 are provided between the first inductive write head pole 118 and the second inductive write head pole 116 for assisting in writing operation. In addition, an overcoat 115 consisting of a silicon layer 12 and a diamond-like carbon (DLC) layer 13 disposed on the silicon layer 12 (refer to FIG. 1f) is covered on surface of the pole tip and surface of the substrate of the slider to protect the slider.
Presently, in structure of above slider, a GMR (giant magneto-resistance) element is used as the MR element to achieve reading operation. However, with continuously increasing demand of larger areal density of a hard disk drive (HDD), currently used GMR element has almost gotten to its extreme limitation to further improve areal density of the HDD, as a result, a new MR element, i.e., a TMR (tunnel magneto-resistance) element, which can achieve more higher areal density than a GMR element, is developed as the next generation of the read sensor of a HDD.
Referring to FIG. 1f, a conventional TMR element 10 comprises two metal layers 11 and a TMR barrier layer 14 sandwiched between the two metal layers 11. An overcoat 115 consisting of a silicon layer 12 and a diamond-like carbon (DLC) layer 13 disposed on the silicon layer 12 is covered on surface of the metal layers 11 and the TMR barrier layer 14 to protect the TMR element 10.
In manufacturing process of a slider, the Magneto-Resistance Resistance (MRR) value of the TMR element must be controlled to a predetermined value so as to maintain good dynamic performance for the slider. For example, in lapping process of the slider, the MR height of the TMR element should be precisely lapped in order to adjust the MR height to a designed value, as the MR height greatly affects the MRR value, thus further affects dynamic performance of the slider and HDD. Take another example, in vacuum process of the slider, the MR height should be kept constant all the time so that the MRR is unchanged.
However, in conventional TMR element structure, since metal layers are in direct contact with the silicon layer of the overcoat, metal material of the metal layers readily diffuses into surface of the silicon layer, and the metal material diffused into the silicon layer functions as an electrically conductive lead, which electrically connects the two metal layers of the TMR element together, thus a shunting path for circuitry of the TMR element being formed between the two metal layers via the metal material diffused into the silicon layer. Unfortunately, this shunting path causes reduction of the MRR value of the TMR element, and consequently degrades dynamic performance of the slider and even read performance of the HDD. It is proved by experiment that after the overcoat is covered on the surface of the TMR element in a vacuum process, the MRR drop thereof is about 4%, and sometime the MRR drop can be dramatically 10%, which is fatal for process control and dynamic performance control of the slider.
Thus, there is a need for an improved system and method that does not suffer from the above-mentioned drawbacks.